If you've never been to a university library in London, you might expect it to be full of nerdy types huddled over grand tomes with a magnifying glass. The reality is boys and girls pristinely clad in next season's wardrobe, shooting flirtatious glances at each other from the parapets of their MacBook Pros.

Over the weekend a new website was launched which should ensure they get even less work done. Fitfinder – think Twitter meets a personal ads column – allows students to proclaim, and potentially contact, their library crushes.

The concept is simple. If you "find a fitty" in the library you can anonymously post up a short description of them on your university's fitfinder. You have the option to describe yourself, or provide a telephone number. Others in the library, including the targeted fitty, are able to comment on the post.

So last night, in UCL's archeology library, one student anonymously posted:

"Female, brunette, tall, dark. I winked, you winked, find me at the same place tomorrow. I'll be wearing a red and blue pinstripe shirt."

Meanwhile in the main LSE library, someone spotted:

"Male, brunette. Curly, waistcoat, bit of a Tory, he's gawwwwgeous!"

The sites have become instantly popular and are getting around 25 posts an hour during the evenings.

Ariella Wollens, a first-year UCL student, told me: "The second a description goes up, you have a look round the library to see who they're talking about. Then everyone bundles in with their own opinions. It's very funny, although I haven't met anyone who's got a date out of it yet."

The site's creator, Rich Martell, a third-year computer science student from UCL, says he took his inspiration from his friends on the rugby team. "When we're revising in the library we all text each other when we see an attractive girl. That planted the idea in my head for a website."

Martell made the site live on Friday. He says he has been surprised by the rapid response, claiming that on Saturday the UCL site had 2000 unique users, which had rise to 8,500 on Sunday and 18,000 on Monday.

He's now set up sites for several other London universities – LSE, Imperial and King's – as well as Oxford and Cambridge, with more set to follow. He also to make money from the sites and is already running targeted adverts for local nightclubs and student deals.

"We're selling the adverts to local business and restaurants near the university – it's perfect for them to advertise to students because they know they're in the area."

Can he see this becoming a full-time profession?

"No, I've got a job in the city lined-up for me. This is only a joke."